save your bacon - to save from injury or loss (material, reputation, etc) - Brewer refers to this expression in his 1870 dictionary so it was certainly established by then, and other etymologists suggest it has been around at least since the 17th century. Brewer says one origin is the metaphor of keeping the household's winter store of bacon protected from huge numbers of stray scavenging dogs. In that sense the meaning was to save or prevent a loss. The establishment of the expression however relies on wider identification with the human form: Bacon and pig-related terms were metaphors for 'people' in several old expressions of from 11th to 19th century, largely due to the fact that In the mid-to-late middle ages, bacon was for common country people the only meat affordably available, which caused it and associated terms (hog, pig, swine) to be used to describe ordinary country folk by certain writers and members of the aristocracy. Norman lords called Saxon people 'hogs'. A 'chaw-bacon' was a derogatory term for a farm labourer or country bumpkin (chaw meant chew, so a 'chaw-bacon' was the old equivalent of the modern insult 'carrot-cruncher'). 'Baste your bacon', meant to strike or scourge someone, (bacon being from the the outside of a side of pork would naturally be imagined to be the outer-body part of a pig - or person - to receive a blow). See also 'bring home the bacon'.